Method of heat treating glass sheets on a gaseous support bed



P- w, 1967 1.c. FREDLEY ETAL .@MHM

METHOD 0F HEAT TREATING GLASS SHEETS 0N A GASEOUS SUPPORT BED Original Filed Nov. L, 1962 17 SheetS-Slneet l W INV NT RS Wm. W, Wm

J. c. FREDLEY ETAL Em METHOD OF HEAT TREATING GLASS SHEETS ON A GASEOUS SUPPORT BED Original Filed Nov. 9, 1962 l? Sheets-Sheet 2 17 J. c. FREDLEY Erm. 3,34%? METHOD OF HEAT TREATING GLASS SHEETS ON A GASEOUS SUPPORT BED Original Filed Nov. 9, 1962 17 Sheets-Sneek 5 @W W, W? J. c. FREDLY ETAL 334.2573

METHOD OF HEAT TREAT ING GLASS SHEETS ON A GASEOUS SUPPORT BED 1962 17 Sheets-Sheet 4 Original Filed Nov. 9,

Hmm. W, 1967 J. c. FREDLEY 5TM 3,3425@ METHOD OF HEAT TREATING GLASS SHEETS ON A GASE'OUS SUPPORT BED Original Filed NOV, 9, 1962 17 ShQetS-Sheet 5 L; KLM; .INVENTORS www@ METHOD 0F HEAT TREATING GLASS SHEETS 0N vA GASEOUS SUPPORT BED 1962 l? Sheets-Sheet 6 Original Filed Nov. 9.

f INVENTUM Mmm* c". www m' w www@ f. ummm-Q J. C. FREDLEY ET AL METHOD 0F HEAT TREATING GLASS SHEETS 0N A GAsEoUs SUPPORT BED 1962 17 Sheets-Sheet 7 Original Filed Nov. 9,

@W 1.o. FREDLEY ETAL MZJWE METHOD OF HEAT TREATING GLASS SHEETS ON A GASEOUS SUPPORT BED 1962 Mm. W, WW! J, FREDLEY HAL EQWE METHOD O EAT ATI GLASS SHEETS ON A GASE SU RT BED Original Filed Nov. 9, 1962 17 ShetS-Shefet 9 O O O O O w. w IN1/ENT@ S JWM-s c. m-2L m camwaf E. smv mw J. c. FREDLEY ET AL METHOD OF HEAT TREATING GLASS SHEETS ON A GASEOUS SUPPORT BED Original Filed Nov. 9. 1962 17 Sheets-Sheet lO INVENTORS ,m-mmf @fo/em' fr sa/aww@ mi 1%? .1.c. FREDLEY ETAL @wmyw METHOD 0F HEAT THEATING GLASS SHEETS 0N A GAsEoUs SUPPORT BED Original Filed Nov. 9. 1962 17 Sheets-$hee1t 11 J C. FREDLEY ET AL METHOD o1"1 HEAT TREATING GLASS SHEETS 0N A GASEOUS SUPPORT BED Original Filed Nov. 9, 1962 l'f Sheets-Sheet 12 @7 .1.c. FREDLEY ETM MW METHOD OF HEAT TREATING GLASS SHEETS ON A GASEOUS SUPPORT BED Original Filed Nov. 9. 1962 l? Sheets-Sheet 1:5

GLASS MOVEMENT 3 mrrmmmmm WV 3, l5! 50 {uml-bww PRESSURE UNIFRNI GAS TEMPERATURE r 63 FOR CQNVEC'HON HEATING AWV \ f/ ll! 0F GLASS SURFACE' MODULE PBESURE PRUH'MJ:

W W/AVERAGE suwoa My,

SRM. 9, 197

J c. EREDLEY Erm BMYB METHOD 01"" HEAT TREATING GLASS SHEETS ON A GASEOUS SUPPORT BED Original Filed Nov. 9. 1962 17 Sheets-Sheet 14 RELATIVE MOVEMENT oF GLASS WITH RESPECT To MODULES UNIFORM SUPPORT PREssu RE- um FORM GAS TEMPERATURE PoR coNvEcTuoN comme 0F GLASS SURFACE AT HLGH cooLmG Rm HEAT TRANSFER RATE PROFILE AVERAGE HEAT SEER RATE JNVENTORS J. c. FREDLEY ET AL 3,342,573 METHOD OF HEAT TREATING GLASS SHEETS ON A GASEOUS SUPPORT BED 1962 Sept. 19, 1967 17 Sheets-Sheet l5 Original Filed Nov. 9.

5 aww/meant W H, im 1,0 FRED Y ET AL zv@ T METHOD 0F HEAT TRE NG GLASS SHEETS ON A GAsEOUs SUPPORT BED Original Filed Nov. 9. 17 Sheets-Sheet le J. c. FREDLEV ET Al. E METHOD OF HEAT TREATING GLASS SHEETS ON A GASEOUS SUPPORT BED 1962 17 SheetS-Sheet 1'7 Original Filed Nov. 9.

United States Patent G Sylvania Original application Nov. 9, 1962, Ser. No. 236,676, now Patent No. 3,223,501, dated Dec. 14, 1965. Divided and this application Dec. 13, 1965, Ser. No. 513,378

This application is a division of our copending application, Ser. No. 236,676 now U.S. Patent 3,223,501, entitled Fabrication of Glass, filed Nov. 9, 1962, which in turn was a continuation-in-part of our copending application Ser. No. 236,103, filed Nov. 7, 1962, now abandone-d, which application is, in turn, a continuation-inpart of our copending application Ser. No. 209,456, tiled July 12, 1962, now abandoned, which application is, in turn, a continuation-in-part of our copending application Ser. No. 185,757, tiled Apr. 6, 1962, now abandoned, which application is, in turn, a continuation-impart of our copending application Ser. No. 172,235, tiled Feb. 9, 1962, now abandoned, which application is, in turn a continuation-in-part of our copending application Ser. No. 139,901., tiled Sept. 22, 1961, now abandoned. Reference is also made to our copending applications Ser. No. 31,572, filed May 25, 1960, now abandoned; Ser. No. 139,902, led Sept. 22, 1961, now abondoned; Ser. No.140,135, filed Sept. 22, 19-61, now abandoned; Ser. No. 175,938, filed Feb. 27, 1962, now abandoned; Ser. No. 176,050, tiled Feb. 27, 1962, now abandoned; Ser. No. 178,997, filed Mar. 12, 1962, now abandoned; Ser. No. 185,448, `tiled Apr. 5, 1962, now abandoned; and Ser. No. 195,- 773, filed May 18, 1962, all of which applications are directed to related subject matter. All of the aforesaid applications referred to herein pursuant to 35 U.S.C. 120 are assigned to the assignee of this application.

This invention relates to the fabrication of glass and more particularly to heating of glass and to the transportation and/or support of hot glass sheets, especially glass at a deformation temperature. It is particularly concerned with such a process when combined with other operations such as bending, tempering, annealing, flattening, or coating such sheets.

Sheets of glass may be fabricated through known manufacturing techniques of bending, tempering, annealing or coating and combinations of such techniques to form end products having characteristics and uses different from the original product. A common feature of these ltechniques is the heating of glass sheets to a temperature above that at which the major surfaces or the contour thereof will be changed by a deforming stress or Contact with solids, hereinafter referred to as deformation temperature. For most plate and window glass this temperature is around 980 degrees Fahrenheit and above, but usually below a temperature at which the glass becomes molten.

Economic utilization of fabricating equipment requires that the glass sheets undergoing treatment be conveyed while hot.

The necessity of conveying glass at high temperature has heretofore resulted in undesirable deformation or marring of the major surfaces of glass sheets being treated due to physical contact with sup-porting and conveying appara-tus while the glass is at elevated temperatures. The instant invention overcomes this defect common to the known methods of heat treating glass sheets. In addition, this invention overcomes further disadvantages peculiar to some of the individual fabricating techniques.

3,342,573 Patented Sept. 19, 1967 ICC Included in the instant invention are new and useful methods and apparatus for supporting and conveying hot glass. More specifically, methods and apparatus have been devised for supporting and conveying a sheet of glass on a lm of gas while the glass is at or above deformation temperature. The film of gas uniformly supports the glass against undesired deformation and eliminates the necessity of contact of the major surfaces of the glass sheet with any solid object while the glass is subject to deformation or impairment. In this manner, the marring or distorting now associated with current flat glass fabricating processes has been eliminated.

Classical bending of fiat glass consists of heating the sheet while supported over a sand mold and allowing the glass to sag until i-t conforms to the mold. Such technique is obviously applicable only to custom jobs and does not lend itself to tempering. Small pieces of flat glass are even today bent on solid asbestos-covered convex molds, particularly in cases where the bends are spherical and the tolerance in surface quality is large. With the advent of curved auto and aircraft lights or windows, there is now demand for large volume production of curved sheet glass of high surface quality. Sometimes the glass is annealed and laminated, sometimes tempered, for safety purposes.

Fabricators of window and plate glass have -utilizer a variety of techniques heretofore for bending auto and aircraft glass. Simple bends have been produced by suspending flat parts with tongs, heating the glass above deformation temperature and applying bending moments by application of weighted wires urging the glass to conform to a predetermined simple curve, also by pressing the glass suspended by tongs with complementary malefemale solid molds. Tongs mar the glass where they engage the surface, as do wires or the solid portions of presses.

Horizontal bending by gravity has been utilized, sheets of glass being mounted singly or in pairs across a ring mold or open affair in which only a small section of the major surface around the periphery of the glass being bent comes into contact with a mold surface and the glass is allowed to sag to shape under the influence of heat, sometimes aided by moments of force applied through movable mold sections. Because the chord of the curve produced is shorter than the same dimension on the at pattern, there is relative movement between mold surface and glass while the glass is soft. This produces mold marks and scutf. Furthermore, the differential in heat capacity between the mold (usually metal) and the surrounding environment sets up differential stress patterns in the glass whether subsequently annealed or tempered and often produces visible distortion called pie crust.. Pie crust is a defect in the glass margins which appears to correspond roughly to the edge of the mold. Usually the glass is conveyed upon the mold during annealing or tempering until fabrication is complete., This requires a large complement of molds to achieve good production rates, another disadvantage.

In utilizing the instant invention for bending, the marring of the surface common to the prior art is overcome. Glass `sheets are supported and conveyed over a gas lilm support while the sheets are heated to a temperature at which they can bend. Due to the substantial uniformity of support pressure provided by the gas hlm yof the instant invention, the contour of the heated sheets may be maintained within close tolerances. By gradually changing the contour of the supporting gas film bed and conveying the heated sheets by edge contact or contact localized at the margins only, the contour of the sheets changes in travel to conform to the supporting force, resulting in sheets forward to a desired curvature. The curved sheets .b so produced may be either tempered or annealed subsequently, while retaining the established contour on the gas film.

In tempering flat sheets, the prior art uses one of three alternative means of support. In one, the glass is gripped near an upper margin by tongs and thus is suspended from a carriage riding on a conveyor which may move the glass from a vertical furnace either laterally or vertically to a position between adjacent blowers which quench or temper the glass. Alternatively, the glass may rest at the bottom edge on a mesh support carried by the conveyor and be held upright by fingers on each side of the upper edge. In a second alternative, fiat glass is simply conveyed through a furnace and thence between horizontal blowers with the bottom major surface of the glass supported on rolls of small diameter closely centered so as to diminish the distance between lines of support.

The vertical processes leaves tong or finger marks and develop uneven stresses attributable to local heat transfer differentials in the vicinity of the mesh, fingers and tongs.

The roller process leaves roll marks, scutf marks, and other defects, in addition to which a certain degree of wave distortion is inevitably imparted to the sheet as a consequence of the glass undulating over the rolls as it softens in its travel.

In the instant invention, glass sheets, for example, fiat sheets, to be tempered, are supported upon a film of gas exerting a substantially uniform pressure so as to support the sheets against deformation while they are heated to a deformation temperature. Such support can be so effectively achieved that even warped sheets can be flattened. The movement of the sheets along the gas support is controlled through physical means contacting only an edge or marginal portion thereof. After reaching the desired temperature, each sheet is moved between a supporting, relatively cold, flowing gas support and an opposing cold gas iiow on the opposite major surface, both having sufficient flow and low temperature to establish the necessary thermal gradient between the -surfaces and the interior, and is thus tempered without the marring or distortion characteristic of the prior art.

In addition to eliminating the foregoing disadvantages, the instant invention, through more efficient and uniform heat transfer, has substantially eliminated the irregular iridescent strain pattern characteristic of tempered glass and has provided a process for fully tempering thinner glass to produce products of higher quality than has been possible under existing production processes.

In known processes of annealing, glass exhibiting undesirably high internal stresses is conveyed on rollers through a lehr where it is reheated substantially toits upper annealing range to allow stresses to relax and is then cooled in =a controlled manner through the lower limit of its annealing range. The nonuniform support and the unavoidable slippage between the rollers and the softened glass results in distortion and surface marring of the sheets. In the manner herein disclosed, glass may be reheated and annealed without the attendant disadvantages of the known processes. This is accomplished by supporting and conveying the heated sheets of glass along a gas film bed which provided uniform support without physical contact with the major surfaces of the glass.

Coated glass has myriad end uses. Many coatings require heat treatment during fabrication. For instance, in producing flat colored spandrels for architectural purposes, at sheet glass is coated cold on one side with a frit or enamel and then tired to glaze the frit and bond it to the glass surface. Firing temperatures exceed the deformation temperature of the flat glass substrate. If produced on roller lehrs, wave, bow and other distortion results. If processed while suspended by tongs, tong marks ensue. lUsually the product is chilled after firing to produce a semi-temper, or partial strengthening. Full temper within practical quality limitations is well nigh impossible of achievement with existing processes because of lack of control. The heat transfer rate on one side of the sheet differs from that on the other. Existing relatively crude quenching blowers do not permit the control necessary to match the quantum of heat transfer on opposite sidesa practical sine qua non for achieving full temper.

Likewise, there is a desideratum for higher temperature in firing because the durability of the coating is enhanced thereby. The prior art is limited in this regard because above about 1150` degrees Fahrenheit, tongs not only indent but more or less tear the glass along the points of contact, while in the roller system intolerable wave results.

The present invention overcomes all these defects. The coated sheet can be fired at higher temperatures without marring or distortion. It can be tempered to the degree desired by control of the rates of flow in the quenching section.

Again, a variety of useful end products are produced by spraying metallic salt solutions on hot glass. Transparent electroconductive tin oxide coatings are produced when a cold solution of a tin salt such as tin chloride is sprayed on hot glass. Transparent light and heat reflecting films are produced when solutions of cobalt and other metal salts are sprayed cold on hot glass. As in the case of enamels, the inadequacies of the prior art limit the temperature of sheet glass treatment below optimum ternperatures desirable in achieving not only maximum durability but other functional attributes such as conductivity in conductive films. The glass is marred and distorted in treatment. These deficiencies are overcome in utilizing the present invention. l Y v Y The broad-'concept of supporting and conveying sheet material on a lm of gas is, of course, known and has been used in many industrial applications. These known methods and apparatus for supporting and conveying sheet material are, however, unsatisfactory for supporting a readily deformable Visco-elastic material while the material approaches a deformation temperature. Because the known methods and apparatus are incapable of'supporting a deformable Visco-elastic sheet of material uniformly over substantially its entire area, their application to the support of glass sheets heated to a temperature at which they readily deform is precluded. Thus, the insufciencies of design for the purposes herein intended of such a gas film support as disclosed in U.S. Patent No. 1,622,817 to Frederic B. Waldron result in an unacceptable .distortion of any glass heated to the temperature at which it will readily deform when supported on a device of the nature disclosed therein.

Applicants have, through the use of the methods and apparatus disclosed herein which form the subject matter of this invention, overcome the above-discussed disadvantages of the known methods of treating, supporting and conveying glass.

In its broader aspects the present invention contemplates the provision of a support system adapted for handling hot glass, or other heat deformable material, in sheet or ribbon form without marring or otherwise producing uncontrolled deformation in the major surfaces, even when the glass or other material is at a deformation temperature.

In accordance with an embodiment of the invention, there is provided a plurality of evenly distributed zones of uniform nominal pressure on the lower side of the sheet adequate to support the sheet element undergoing treatment. Gas flows from a reservoir under higher pressure into such zones, being uniformly throttled between the reservoir and each zone to restrict the passage of gas between the two. Each zone constitutes a unit of support area with respect to the sheet to be supported and each has a reference surface at its margins common to the remainder. Within each zone, gas entering from the reservoir is diffused after throttling so as to avoid creation of localized jets normal t-o the reference surface and otherwise to equalize pressure and liow under normal conditions of operation. Provision is made for escape of the ow of gas emanating from each zone when covered by glass. In operation, the rate of flow of gas from the reservoir to each zone is maintained at such level that the average clearance between the reference surface and the glass sheet being supported is not less than 0.001 inch and not greater than 0.050 inch, normally not greater than 0.025 inch for glass having a thickness of 1A; inch and above, and in any case never more than 50 to 90 percent of the thickness of the supported glass.

More particularly, the invention contemplates such a gas support system in which glass is introduced onto the support area at a temperature below that at which its major surfaces will mar on physical contact with solid objects, the glass is heated above deformation temperature while supported primarily by gas and is then cooled until below deformation temperature before removal from the gas support. The system is particularly well adapted to heating iiat glass in the form of sheets or the like in which the thickness ranges up to 1K2 to one inch and the length and breadth of the sheet generally are over 6 inches or one foot to as much as 5 or 10 feet or greater, optionally bending it by travel over a curved bed, then rapidly Cooling the surfaces or quenching by utilizing relatively coldgas as the support medium, supplementing the cooling effect on the supported side by complementary iiow of cold gas against the opposite side to equalize the heat transfer from the two major surfaces until the entire body is cool enough to prevent loss of temper or, in other words, redistribution of the stress differential set up between the surfaces and the interior of the glass body by diiferential rates of cooling.

Advantageously, heating of glass-upon the gas support is accomplished by burning a controlled admixture of gas and air, introducing the 'hot products of combustion tothe reservoir or plenum chamber which supplies the supporting zones, and supplementing the heat thus supplied to the glass by radiant heat from an independently controlled source or sources which are generally disposed on the side of the glass oppoiste the supported side.

The attendant advantages of this invention and the various embodiments thereof will Abe' readily appreciated as the same become better understood by reference to the following detailed description when considered in connection with the accompanying drawings in which:

FIGfl is a perspective, partly schematic, view illustrating a system for conveying, heating and quenching sheet glass parts embodying several features of the present invention; FIG. 1A is an-other partly schematic perspective on va larger scale illustrating particularly how sheet glass parts are driven by discs contacting an edge of the part while it is otherwise supported entirely by a gas lilm over the inclined bed of FIG. l;

FIG. 2 is a detailed view elevation taken along the line 2-2 of FIG. 1;

FIG. 3 is a partial plan view showing the arrangement of the preheat section with respect to gas iilrn support heating section, the relative positions lof the burners feeding combustion gases to the plenum chambers and the mechanism for conveying glass sheets by edge contact only; i

FIG. 4 is a partial plan view which is in eiect a continuation of FIG. 3 1and shows the terminus of the gas iihn support heating section adjacent the quenching section, the latter being followed by the conveyor roll run out sections; l

FIG. 5 is a side elevation of the quenching system showing the relationship of the upper and lower heads;

FIG. 6 is an end elevation of the system of FIG. 5;

FIG. 7 is a sectional view partly in elevation taken along the line 7-7 of FIG. 1'.

FIG. 8 is a schematic view showing the arrangements for supplying air and cooling water to the quenching heads;

partly in section and partly in FIG. 9 is an approximately full scale sectional detail illustrating elements of quenching module design and patterns of air iiow during operation;

FIG. l0 is a sectional detail showing the arrangement for supplying air to those quenching modules in the row next adjacent to the heating section;

FIG. l1 is a partially detailed plan view of the first and second beds in the gas support heating section showing the relationship of the individual modules in the geometry of the mosaic;

FIG. 12 is a sectional view taken along line 12-12 of FIG. ll, showing the relationship of the modules and exhaust ducts to the bed plate and plenum chamber;

FIG. 13 is an enlarged partial plan view of the lower quenching bed of FIG. 4;

FIG. 14 shows the arrangement used to vary the speed of the conveyor drive during the run out of parts from the heating to the quenching section;

FIG. 15 is a perspective view showing a gas film support bed, the generative surface of which progressively changes in contour from flat to a cylindrical shape in a cross section normal to the longitudinal axis of the bed;

FIG. 16 is an end elevation of the bed of FIG. l5 vlooking toward the p-art of maximum curvature;

FIG. 17 is a side elevation of the bed of FIG. 15 showing how the curve is developed along the path of travel of the glass;

FIG. 18 is an elevation of the burners, gas and air feeds and controls for one of the three plenum chambers 'of the gas support heating section;

FIG. 19 is a schematic view on enlarged scale of a section of the gas support bed showing diagrammatically the liow and exhaust of the support gases and presenting diagrammatic graphs in conjunction therewith;

FIG. 20 is a View similar to FIG. 19, presenting diagrammatic graphs and flows in conjunction with the `quenching system; A

FIG. 21 is a plan'view approximately double scale illustrating a prototype support module unit;

FIG. 22 is a section taken along the: line 22-22 of FIG. 2l; i g A FIG. 23 is a plan view double scale of an improved support module unit, simpler of fabrication and'in which the support area is subdivided by partitions;

FIG. 24 is a section taken along lines 24-24 of FIG. 23;

FIG. 25 is a plan view approximately double scale of a typical quenching module unit;

FIG. 26 is a section taken along lines 26-26 of FIG. 25;

FIG. 27 is a plan view of a quenching module unit having a step in the marginal walls to enhance turbulence of the quenching gases at the gas-glass interface;

FIG. 28V is a section taken along lines 28-28 of FIG. 27;

FIG. 29 is a plan View approximately double scale illustrating a support module unit having a circular cross section in the plane of support;

FIG. 30 is a section taken along line 30-30 of FIG. 29;

FIG. 31 is a partial plan View of a module bed of the module units shown in FIGS. 29 and 30;

FIG. 32 is a partial plan view of support modules arranged in rows with alternate-longitudinal exhaust grooves; and v FIG. 33 is a section taken along line 33-33 of FIG. 3l.

Referring to the drawings, FIG. 1 illustrates a system advantageously employed for heating liat glass parts up to or above the deformation temperature, eg., to a ternperature at which the glass can be tempered, quenching such parts while hot and delivering the parts thus tempered onto a roll conveyor for removal. The Component sections making up the complete system consist of a preheat section 1 wherein the glass is conveyed on rollers between radiant heaters to preheat the glass until brought to a suitable preheat temperature under the deformation 

